Sortation Conveyor Apparatus and Methods

ABSTRACT

Sortation conveyor apparatus and methods for selectively diverting articles from a primary conveying surface onto branch lines are provided. In one embodiment, the apparatus comprises a control system for selectively operating activating elements. The control system is configured to assign two or more pusher elements to each article to be diverted, and to ensure proper diversion of articles when adjacent articles are spaced apart on the primary conveying surface by a distance which is less than the width of an individual pusher element. In one embodiment, diversion is provided by a single activating mechanism for a plurality of pusher elements per branch destination, and by rotating the article during the initial diverting movement and contact with the pusher elements. In one embodiment, a method comprises assigning memory cells to first and second articles based upon the location of the articles along the primary conveyor, and determining if the second article is to be diverted to the same location as the first article, and if so, assigning the trailing cell assigned to the trailing end of the first article to other than the first article.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 60/800,167, filed May 12, 2006, and U.S. ProvisionalPatent Application No. 60/834,387, filed Jul. 31, 2006, the entiredisclosures of which are considered as part of the disclosure of thepresent application and are hereby incorporated by reference herein.

FIELD OF THE INVENTION

The present invention is directed to sortation conveyor apparatus andmethods.

BACKGROUND OF THE INVENTION

In conveyor systems for conveying and distributing articles, a series ofconveyed articles are typically transported along moving conveyingsurfaces. Such conveyor systems will typically include one or moresortation devices which divert selected articles from a primaryconveying path onto one or more secondary conveying paths.

Sortation devices often employ pusher elements which are mountedrelative to the conveying surface. Often, the pusher elements aremounted such that they may be selectively moved across the conveyingsurface in order to eject an article from the primary conveying pathonto a secondary conveying path or other location. One particularsortation device of this type is referred to as a “shoe sorter,” whereinthe pusher elements are termed “shoes.”

In a typical shoe sorter, the primary conveying surface is provided by aplurality of transverse tubes (rollers) or slats that form the transportsurface. A plurality of pusher elements that are part of, or supportedby, the transport surface and are guided in a set position along thelength of the sorter during normal forward operation. The pusherelements can take on many forms such as belted slats, pins, and moldedblocks. Historically the most prevalent design is referred to as a shoe,although other designs are possible. Here after the term shoe and pusherelement shall be used to include all conventional shoes, as well asother diverting elements such as but not limited to slats, belts,rollers, etc. When it is necessary to direct an article from the mainconveyor run to an adjacent takeaway conveyor, a switch mechanism causesan assigned set of pusher element to be diverted to slide across theconveyor surface in a diagonal direction. The diverted shoes thus engageand divert the article to a secondary conveying path, such as a takeawayconveyor. Such shoe sorters often use guide tracks or guide surfaceswhich direct the assigned set of shoes laterally across the conveyingsurface, while shoes which are not assigned continue to travel along theconveying surface in their set position.

In these shoe sorters and other types of sortation devices, the controlsystem ensures that the appropriate set of pusher elements is assignedto each carton, and that the assigned pusher elements are directedacross the primary conveying surface at the proper time. Sorterthroughput depends on a variety of factors, particularly the speed ofthe conveying surface and the size of the gap between adjacent articlesbeing sorted. If the size of the gap is small, it can be difficult forthe control system to not only assign the proper set of pusher elements,but also ensure that the assigned set of pusher elements are divertedacross the conveying surface at the proper time.

SUMMARY

According to one embodiment, a sortation conveyor apparatus is providedfor selectively diverting articles from a primary conveying surface ontoone of a plurality of branch lines. The apparatus comprises a drivenprimary conveying surface configured to support and transport articlesthereon, two or more branch lines extending away from said primaryconveying surface, and a plurality of pusher elements mounted formovement with said primary conveying surface for selective movementacross said primary conveying surface so as to selectively divertarticles onto said branch lines. The apparatus further comprisesactivating mechanisms configured to move said pusher elements acrosssaid primary conveying surface, a single activating mechanism beingconfigured to move a plurality of pusher elements. The apparatus furthercomprises a control system for selectively operating the activatingmechanisms. The control system is configured to assign two or more ofsaid pusher elements to each article to be diverted, and to selectivelyoperate the activating mechanisms when the assigned pusher elements arelocated adjacent a predetermined branch line for the article to whichthe pusher elements are assigned. The control system is also configuredto ensure proper diversion of articles when adjacent articles are spacedapart on the primary conveying surface by a distance which is less thanthe width of an individual pusher element.

According to another embodiment, a method for transporting items on aconveyor system is provided. The method comprises receiving destinationsfor a plurality of articles to be sequentially transported in a primaryconveying direction on a primary conveyor system. The primary conveyorsystem comprises pusher elements provided along the primary conveyorsystem and configured to move articles in a direction different than theprimary conveying direction to selectively divert articles to branchdestinations off of the primary conveyor system. The method furthercomprises spacing the articles apart on the primary conveyor system inthe primary conveying direction, wherein the spacing of at least twoadjacent articles is less than the width of a pusher element, andassigning some of the pusher elements to each article. The method alsocomprises providing a signal based upon the location of an article as ittravels in the primary conveying direction, wherein the signal isconfigured to move pusher elements assigned to the article at anappropriate location along the primary conveyor system to cause thearticle to be moved in a direction different than the primary conveyingdirection and to rotate upon initiation of the movement, to therebydivert the article to their corresponding branch destinations off of theprimary conveyor system.

In one embodiment, a computer implemented method for controlling aconveyor system is provided, the method comprising receivingdestinations for a plurality of articles to be sequentially transportedalong a primary conveyor system, and providing in memory cellsrepresenting locations along the primary conveyor system. The primaryconveyor system comprises pusher elements for diverting articles tobranches off of the primary conveyor system. The method furthercomprises assigning cells to first and second articles based upon thelocation of the articles along the primary conveyor system, wherein thefirst and second articles are adjacent one another, determining if thesecond article is to be diverted to the same destination as the firstarticle, and if so, assigning a trailing cell assigned to the trailingend of the first article to other than the first article. The methodfurther comprises using the cell assignments, providing signals toactivate pusher elements at corresponding locations along the primaryconveyor system to divert the first and second articles to destinationsoff of the primary conveyor system.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description will be more fully understood in viewof the drawings in which:

FIG. 1 is a perspective view of a shoe sorter in accordance with oneembodiment of the present invention;

FIG. 2 is a schematic, top plan view of a shoe sorter in accordance withone embodiment of the present invention;

FIG. 3 is a schematic illustration of a data array used by the controlsystem of a shoe sorter in accordance with one embodiment of the presentinvention; and

FIG. 4 is a flow chart depicting the assignment of shoes to cartons bythe control system of a shoe sorter in accordance with one embodiment ofthe present invention.

The embodiments set forth in the drawings are illustrative in nature andare not intended to be limiting of the invention defined by the claims.Moreover, individual features of the drawings and the inventions will bemore fully apparent and understood in view of the detailed description.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention is directed to sortation conveyor apparatus andmethods which can accommodate reduced gap size between adjacent conveyedarticles. By reducing the size of the gap between articles delivered tothe sortation conveyor apparatus, article throughput may be increasedfor a given conveying speed. In other words, articles to be sorted maybe inducted onto the sortation conveyor apparatus with a smaller gapbetween adjacent articles. While the present invention will be describedin connection with a shoe sorter of the type shown and described in U.S.Pat. No. 4,884,677 (“the '677 patent,” which is incorporated herein byreference), the present invention, particularly the methods and controlsystems described herein, may be used in conjunction with other types ofsortation devices. For example, the shoes or pusher elements maycomprise belt and/or follower elements of a linear belt sorter, such asof the type described in U.S. Pat. Nos. 6,669,001 and 6,854,584 andCanadian Patent No. 2,448,133, which are hereby incorporated herein byreference. As another example, the primary conveying surface may beprovided by tubes (rollers) or slats extending transverse to thedirection of travel of articles moving on the primary conveying surface.Of course other types of conveying surfaces may be employed. Inaddition, the pusher elements (e.g., shoes) described herein may haveany of a variety of shapes and configurations which allow the pusherelements to be selectively pushed across the primary conveying surface.

In general, embodiments of the sortation conveyor apparatus of thepresent invention may include a main conveying line along which articlesare transported in a forward direction. The apparatus provides selectivediversion of the articles as desired onto branch conveying linespositioned at strategic points along the sides of the main conveyor. Themain conveyor may include a frame which supports the primary conveyingsurface. The conveying surface may support a plurality of pusherelements (e.g., divert shoes, belts, etc.) that are mounted to allow forlateral shifting across the conveying surface (e.g., transverse to theprimary conveying direction). For example, the divert shoes maygenerally travel with the primary conveying surface in the primaryconveying direction along either of opposing sides of the conveyingsurface when the sorter is operating in a straight-through mode, i.e.the article is moving forwardly for later downstream handling.Alternatively, as will be described in more detail below, the divertshoes may be selectively diverted to slide across the transport surfacein a diagonal path in the divert mode to engage and direct articles ontoa branch conveying line (e.g., onto a takeaway conveyor).

Guide tracks or surfaces may be mounted to the conveyor frame beneaththe conveying surface to engage a guide member extending from eachdivert shoe so as to guide the shoes in either the forward directionwhen in straight-through mode or, alternatively, diagonally across thetransport surface when in the divert mode. In order to initiate thedivert mode, a divert switch apparatus may be provided at selectedpositions along the conveyor (i.e., at divert stations associated witheach branch line). The divert switch apparatus intercepts the divertshoes when actuated and directs them toward the predetermined diagonalpath necessary to direct an article to the selected takeaway conveyor. Acontrol system is used to determine which shoes should be diverted ateach divert station in order to direct each article onto the properbranch line.

In particular, FIGS. 1 and 2 depict a sortation conveyor apparatusaccording to one embodiment of the present invention, specifically, ashoe sorter 10. Shoe sorter 10 includes a frame generally designated as11 which defines the main conveying line 12. Branch outlets 13 and 13′connect with branch lines 15 and 15′, respectively. An endless apron 20is supported for driven movement on the frame 11 and defines the primaryconveying surface which moves from right to left in FIG. 2. In theembodiment shown, the apron 20 comprises a pair of roller chains, andmultiple parallel cross tubes 22 carried by the chains in spacedrelation with each other lengthwise of the apron so that the uppermostportions of these tubes define a discontinuous surface in a horizontalplane on which packages are supported and conveyed. Of course theconveying surface may be provided by any of a variety of otherstructures known to those skilled in the art, such as a plurality ofinterconnected slats in place of the cross tubes 22 (as described, forexample, in U.S. Pat. No. 5,217,105, which is incorporated herein by wayof reference). It also will be understood that any number of branchoutlets and branch lines can be provided, as desired.

Articles (e.g., cartons, packages, products, etc.) to be sorted may bedelivered to shoe sorter 10 in a variety of ways. For example, aninduction conveyor 151 may be provided in order to deliver a series ofarticles (e.g., cartons) to the sortation conveyor apparatus. Thecartons are typically arranged in a single file line along the inductionconveyor, with a gap between adjacent cartons. This gap may be the samefor adjacent cartons, or may vary. In addition, the induction conveyoritself (or another device(s) known to those skilled in the art) may beused to set the gap between adjacent cartons to a predeterminedvalue(s), if desired.

The purpose of the shoe sorter is to receive a series of cartons (orother articles) and to selectively direct cartons to one or morelocations. In the shoe sorter shown in FIGS. 1 and 2, cartons deliveredby induction conveyor 151 travel along the main conveying line 12 (i.e.,on conveying surface 20) and are selectively diverted onto one of thebranch lines 15 and 15′. Not all of the cartons need be diverted, assome may continue on downstream of the shoe sorter. A takeaway conveyormay also be provided on each branch line (e.g., a moving belt, drivenrollers, etc.) in order to transport diverted cartons along the branchline, away from the main conveying line. The operation of the shoesorter is automated in that destination information for each carton maybe read (e.g., by a bar code scanner) upstream of the shoe sorter 10,and a control system of the shoe sorter utilizes the destinationinformation to divert each carton onto the appropriate branch line.

Cartons may be selectively diverted from the main conveying line ontoone of the branch lines using pusher elements 25 which are selectivelymoved across the conveying surface 20 at divert stations (17 and 17′)located adjacent to each of the branch outlets. In one embodiment, eachpusher element 25 (also referred to as a shoe) is mounted for slidingmovement on each pair of adjacent cross tubes 22, as shown in FIG. 1herein and as further described in the '677 patent. In embodiments usingslats instead of cross tubes, each shoe may be mounted for slidingmovement on one or more of the slats which provide the primary conveyingsurface of the shoe sorter.

During operation, the shoes 25 are retained along either the right-handor left-hand side of apron 20, as seen in FIG. 1, and travel with thecross tubes or slat on which each is mounted. When a carton traveling onthe apron approaches a position (i.e., a divert station) which isopposite the branch outlet through which it is to be diverted, the shoes25 traveling on the apron beside that package are diverted such thatthey move across the apron in such timed relation that they push thecarton through the branch outlet onto the branch conveyor line. Eachdiverted shoe slides along the cross tubes or slat upon which it ismounted.

The shoes may be provided in any of a variety of shapes andconfigurations. In one embodiment, and as further described and depictedin the '677 patent, each of the shoes may include a guide pin (33 inFIG. 9 of the '677 patent) which extends downwardly away from the bottomsurface of the shoe. The guide pin may be centered with respect to theshoe, and may carry a bearing (35 in FIG. 9 of the '677 patent)positioned immediately below the bottom surface of the shoe.

As previously noted, each of the shoes 25 is retained along theright-hand or left-hand side of apron 20. This may be accomplished, forexample, by means of a channel shaped guide (60 in FIGS. 2 and 4 of the'677 patent) which is proportioned to slidably receive the end of eachguide pin. A similar pin guide channel (62 in FIG. 2 of the '677 patent)is provided along the left-hand side of the apron.

At each divert station (17 and 17′), a switch assembly may be provided,as well as at least one guide member (or guide channel) for directingdiverted shoes laterally across the conveying surface. For example, anangle member (127 in FIG. 2 of the '677 patent) may be provided beneathapron 20 and extend at an angle with respect to the direction of travelof apron 20. When activated, the switch assembly diverts shoes away fromthe guide channel in which the guide pin of the shoe is traveling. Forexample if the shoes are moving towards a divert station along theright-hand side of apron 20 (e.g., FIG. 1), the switch assemblyselectively diverts shoes to the left such that, for example, thebearing on the guide pin contacts the angle member (as further describedin the '677 patent). As a diverted shoe continues to move forward withthe apron, the bearing of the diverted shoe will continue to travelalong the angle member. This results in the diverted shoe moving to theleft along the slat or rollers on which it sits until the shoe reachesthe left-hand side of the apron 20. By way of example, the guide pin ofthe shoe may enter a second pin guide channel provided along theleft-hand side of the apron (as described in the '677 patent).

As long as the switch mechanism remains activated, successive shoes arediverted sequentially in the same manner, as they reach the switchmechanism, such that a line of shoes extends diagonally across theapron. A carton located on apron 20 adjacent such diverted shoes willthus be diverted into the branch outlet at the divert station. Thismethod of article diversion may also be performed in the same manner forright-hand diverting.

As best seen in FIG. 2, diverted cartons will also rotate or turn asthey are diverted, and immediately upon contact between a diverting shoeand the carton. This occurs because, as the diverted shoes travel acrossthe primary conveying surface 20 (i.e., the apron), a downstream shoewill always be located further to the left than the adjacent shoeupstream. In this method and system, only a single switch mechanism andguide track are used for each branch outlet, and each shoe willsequentially reach the switch during travel of the shoes along with theconveying surface. Accordingly, each shoe will sequentially divert andcontact the carton, from near its leading edge to near its trailingedge, causing rotation to the carton and diverting it along the branchline. Multiple diverting or activating mechanisms (switch mechanisms,tracks, or motors, etc.), and the expenses thereof, are therefore notneeded for each pusher element in this embodiment. As the conveyingsurface rotates underneath and back towards the upstream end of the shoesorter, shoes that were diverted are returned to the opposite side ofthe conveying surface in order that such shoes are available to repeatthe sortation process.

A control system is also provided in order to direct the sortationprocess. In particular, the control system generally comprises at leastone controller and sensors in communication therewith. For each articlewhich is to be diverted, the control system assigns shoes to thatarticle. The control system then actuates the switch assembly of theappropriate divert station when the first of the assigned shoes reachesthe divert station adjacent the branch line onto which the associatedarticle is to be diverted. In one embodiment, the control systemincludes a central controller (160 in FIG. 2) which controls the firing(i.e. activating) of the diverter switch mechanisms in order to directcartons to the appropriate branch conveyor line.

Central controller 160 may be provided in a variety of forms, andprocesses signals provided by one or more devices (such as photosensors,scanners, readers, sensors, etc.), in accordance with one or more setsof instructions, and outputs signals which direct the operation of theshoe sorter. By way of example, central controller 160 may comprise anydevice (or combination of devices) which is capable of processing datain accordance with one or more sets of instructions. For example,central controller 160 may include a processor (e.g., a CPU), as well asmemory which, among other things, stores data and instructions (i.e.,software). Examples include a personal computer, general purposecomputer, workstation, server, mainframe, embedded system,microprocessor, programmable logic controller (PLC), discrete logicsystem, and the like (including combinations of two or more of theforegoing). Central controller 160 processes data provided by, forexample, photosensor 161 in order to generate signals for use inactuating the switch assemblies at the proper time in order to properlydivert articles onto the appropriate branch line.

While a controller or other control mechanism/device may be provided ateach divert station (with or without a central controller), the centralcontroller may be in direct communication with the switch assemblies ateach divert station such that local controllers are not needed. In suchembodiments, the central controller determines when each switch assemblyis actuated and disabled in order to properly divert shoes and cartonscontacted by the diverted shoes.

In the embodiment shown, a local control module (17 and 17′ in FIG. 2)is provided at each divert station. Each local control module maycomprise, a controller of the type described above with respect to thecentral controller (e.g., a processor and memory). In the embodimentshown, however, local control modules 17 and 17′ merely ensure that thedivert switch at that station is fired (i.e., actuated) between theguide pins of adjacent shoes, as further described herein. The localcontrol modules play no other role in the control system of the shoesorter embodiment shown in FIGS. 1 and 2.

Cartons (or other types of articles to be sorted) proceed towards shoesorter 10 along induction conveyor 151. The cartons are typicallyarranged in a single file line along the induction conveyor, with a gapbetween adjacent cartons. While the gap may be the same or different foreach pair of adjacent cartons, embodiments of the present inventionallow the gap to be smaller than what was previously possible. In fact,the gap may be shorter than the width of a single shoe. (As used herein,the width of shoe refers to the center-to-center distance of adjacentshoes, and therefore includes the small gap present between adjacentshoes.) In some embodiments, the center-to-center distance of adjacentshoes in the primary conveying direction is five inches. Accordingly, insome embodiments, adjacent cartons can be spaced less than five inchesapart in the primary conveying direction (e.g., from their closestpoints). Moreover, in some embodiments, adjacent cartons can be spacedin the primary conveying direction four or fewer inches apart, three orfewer inches apart, two or fewer inches apart, and one or fewer inchesapart. The control system is configured to assign sufficient shoes to acarton for proper diverting, while also ensuring that the assignedshoes, when diverted across apron 20 at the proper divert station, willnot contact a trailing carton which is not supposed to be diverted atthat divert station. In this manner, shoe sorter throughput may beincreased without increasing sorter speed (i.e, the speed of the primaryconveying surface, or apron 20). It should be pointed out, however, thatthe rotation of cartons as they are diverted (see, e.g., FIG. 2) doesact as a limit on how small the gap between adjacent cartons can be.

Destination information for cartons or other articles delivered to theshoe sorter (e.g., by induction conveyor 151) may be provided to thecentral controller 160 in a variety of ways. For example, destinationdata (i.e., which branch line, if any, a particular carton is to bediverted onto), may be manually input into the central controller orinput as a data set (e.g., a data file) which was previously created.Alternatively, in the embodiment shown, a destination detecting device155 (FIG. 2) in communication with central controller 160 may beprovided, such as adjacent induction conveyor 151. By way of example,the destination detecting device 155 may comprise an optical scanner(e.g., a bar code reader) which scans a portion (e.g., a region of thecarton on which is printed a bar code) of each carton or a tag or labelaffixed to the carton, as each carton passes by the scanner.Alternatively, the destination detecting device may comprise a readerwhich detects identifying information associated with each carton. Sucha reader may comprise, for example, an RFID reader which acquires datafrom an RFID tag (active or passive) associated with (e.g., within, uponor attached to) each carton. The signal(s) provided by the destinationdetecting device to the central controller may represent not onlydestination data for each carton inducted onto the primary conveyingsurface 20 of shoe sorter 10, but also other carton data (e.g., cartonsize or other useful information). The destination data for a cartonindicates which branch conveyor line, if any, each carton is to bediverted onto.

A sensor 161, such as a photosensor, may also be provided at apredetermined point upstream of, or along the primary conveying path ofshoe sorter 10. In the embodiment shown, photosensor 161 is locatedimmediately upstream of shoe sorter 10, adjacent induction conveyor 151,and is in communication with central controller 161. Photosensor 161detects the leading and trailing edges of each carton passing by thephotosensor. As discussed further herein, additional photosensors 28 and28′ may also be provided at or adjacent to the switch assembly of eachdivert station in order to, for example, detect passage of the bearingon the guide pin of each shoe which passes by. Of course other types ofsensing devices may be used to sense the leading and trailing edges ofcartons and the passage of divert shoes (or portions thereof, such asthe guide pins or guide pin bearings).

Central controller 160 uses the signals from the destination detectingdevice 155 and the article sensor 161 in order to effect actuation ofthe divert switch mechanisms at the proper time, in accordance withstored instructions (e.g., software). The control system software takesinto account the gap between adjacent cartons and whether or notadjacent packages are being diverted to the same branch conveyor line.

As described in more detail below, central controller 160 tracks cartonsas they move through the shoe sorter. When a carton arrives at thedivert station associated with the branch line onto which that carton issupposed to be diverted, central controller 160 sends an “enable” signalto the local control module of that divert station. In response, thelocal control module actuates the switch mechanism.

In one embodiment, however, the switch mechanism is not necessarilyactuated immediately upon receipt of the enable signal from the centralcontroller. Rather, the local control module actuates the switchmechanism so as to ensure that the switch is actuated between shoe guidepins. For example, photosensors 28 and 28′ may be positioned so thatthey are able to detect the passing of each shoe guide pin, particularlythe bearing on each shoe guide pin. In one embodiment, photosensors 28and 28′ may be positioned beneath or adjacent apron 20 so that they areable to detect the passing of the guide pin bearing on each shoe.Photosensors 28 and 28′ may be provided in communication with localcontrol modules 19 and 19′, respectively, as well as central controller160. Photosensors 28 and 28′ may simply provide a signal which indicateswhether or not the photosensor is blocked by a guide pin bearing (e.g.,an ON signal when blocked and an OFF signal when not blocked, or viceversa).

The local control module uses the signal from divert station photosensor28 to determine when to actuate the switch mechanism following receiptof an enable signal from central controller 160 so that the switch isonly fired between shoe guide pins. The manner in which this is done maydepend, for example, on the location of photosensors 28 and 28′ withrespect to the switch mechanism of the associated divert station, aswell as the speed of the conveying surface 20. For example, once thelocal control module has received the enable signal from centralcontroller 160, the local control module 19 may actuate the switchmechanism on the next triggering edge of bearing. The triggering edgemay simply correspond to the moment that the photosensor signal changesstate—from OFF to ON, or from ON to OFF. Thus, depending on the speed ofthe shoe sorter and the location of the photosensor, the local controlmodule, after receiving the enable signal from central controller 160,may actuate the switch upon receipt of an OFF or an ON signal from theassociated photosensor 28. In this manner, the local control moduleensures that the switch is actuated between the guide pins on adjacentshoes.

Following switch actuation, the switch remains open for a period of timeso that the appropriate number of shoes are diverted along the track 21for the carton being directed onto the branch line. In one embodiment,at least two shoes are always diverted for each carton. With or shortlyafter the enable signal, the central controller may send a signal to thelocal control module indicating how many shoes are to be diverted. Thelocal control module may then count how many guide pin bearings aredetected by photosensor 28, based on the signal received from thatphotosensor. Once the appropriate number of guide pin bearings have beendetected, the local control module closes (i.e., disables) the switchmechanism, thereby preventing subsequent shoes from being diverted. Inthis manner, the carton is properly diverted onto the branch line by themovement of the series of shoes across the conveying surface.

Alternatively, central controller 160 may receive signals from the localphotosensors (28 and 28′), and count the number of shoes followingswitch actuation. After the appropriate number of shoes (i.e., guide pinbearings) have been detected, central controller 160 may disable (i.e.,close) the switch, either directly or by sending a signal to the localcontrol module. In fact, in some embodiments, the local control modulesmay be eliminated entirely and the central controller will controlactuation and disablement of the switch mechanisms.

The number of shoes diverted for any given carton must, of course, besufficient to complete the operation of pushing the carton through theappropriate branch outlet. This may be accomplished by “assigning” shoesto each carton to be diverted. Then, when the first assigned shoereaches the divert station for that carton, the switch at that divertstation is actuated. In one embodiment, the first shoe which, ifdiverted, would contact the front edge of the carton is assigned to thatcarton and identified as the “lead shoe”—i.e., the first shoe which isdiverted for a given carton. All of the shoes following the lead shoewhich, if diverted, would contact the carton, are also assigned to thatcarton. The shoes assigned for a given carton also will typicallyinclude the last shoe which, if diverted, would contact the carton, aswell as a predetermined number of trailing shoes following that lastshoe. These trailing shoes (e.g., one, two, three, or perhaps more) areincluded in the series of shoes which are diverted for a given carton,even though these trailing shoes normally will not actually contact thecarton as they move across the apron. One purpose of the trailing shoesis to ensure that a carton does not spin off of the shoes while beingdiverted. However, as further discussed herein, the control system ofthe present invention is configured to cancel one or more of thetrailing shoes, or even the last shoe which will contact a carton ifdiverted, if it is determined by the central controller that thosetrailing shoes (or even the last carton contacting shoe) will contactthe upstream carton if diverted.

The central controller is responsible for “assigning” shoes to eachcarton. The assigned shoes are those which are to be diverted at theappropriate divert station in order to push the carton onto the properbranch conveyor line. The central controller, however, does not assignany type of identifier (e.g., a number or other identifier) toindividual shoes. Instead, the central controller simply assigns shoesto a carton and then monitors the travel of the assigned shoes as theyprogress along the length of the shoe sorter. At the moment the centralcontroller determines that the lead shoe assigned to a carton arrives(or is about to arrive) at the divert station for that carton, theenable signal is sent to the local control module of that divertstation.

In one embodiment, shoes may be “assigned” to each carton in thefollowing manner. The distance from each divert station, particularlythe switch mechanism thereof, to the induction point (see FIG. 2) ismeasured as a multiple of the width of each shoe. For example, thedistance from the induction point (i.e., where the induction conveyormeets the conveying surface of the shoe sorter) to the switch mechanismof the first divert station 17 might be four shoe widths, and thedistance to the switch mechanism of the second divert station 17′ nineshoe widths. By measuring distances in this manner, shoes may be“assigned” to cartons without the need for uniquely identifying eachindividual shoe.

In particular, the software associated with the central controllerestablishes a data array which tracks the location of shoes as they movethrough the shoe sorter. This data array may generally comprise two rowsof cells. The number of columns will depend on the length of the shoesorter, particularly the distance from the induction point to the lastdivert station.

As shown in FIG. 3 which is a simplified illustration of this dataarray, one row of the data array (in the depicted example, the bottomrow) simply comprises a sequential series of integers which correspondto locations along the length of the primary conveying surface. Forexample, the first divert station is arbitrarily identified as 50. Eachcell in the lower row of the data array is also defined to have a widthequal to the width of each shoe (the center-to-center distance betweenadjacent shoes). Thus, in the example wherein the switch mechanism ofthe first divert station is located four shoe widths from the inductionpoint, the induction point corresponds to the cell containing numeral 46in the data array. Similarly, the switch mechanism of the second divertstation corresponds to numeral 55 in the bottom row of the data array.The upper row of cells in the data array generally correspond to shoesas they travel the length of the primary conveying surface 20 of shoesorter 10. As the shoe sorter is operating and the shoes travel thelength of the primary conveying surface 20, the position of particularshoes move from right to left in the sample data array of FIG. 3. Sincethe number of columns in the data array is dependent on the length ofthe shoe sorter (which is less than the total number of shoes multipliedby shoe width), typically less than half of all shoes will berepresented by a cell in the upper row of the data array at any giventime.

In order to simplify the description of the process of assigning shoesto individual cartons, photosensor 161 in the exemplary embodiment islocated at the induction point. (However, the photosensor could belocated at any point upstream of the first divert station). At time T1,the leading edge of carton B is detected by the photo sensor and thedivert location for carton B was previously (or contemporaneously)determined by the destination detecting device 155 and provided tocentral controller 160 (or otherwise provided to the centralcontroller).

As shown in FIG. 3, when the leading edge of carton B is detected, thecell in the data array located immediately above numeral 46(corresponding to the induction point) is identified as being assignedto carton B (e.g., by placing some form of carton identifier in the cellof the data array). Since the cells in the upper row of the data arraygenerally correspond to the location of a portion of the shoes, the cellabove numeral 46 which is assigned to carton B corresponds to the firstshoe which would contact the front (or leading) edge of carton B if thatshoe is diverted. If the divert location for carton B is not the same asthe divert location for the previous (i.e., downstream) carton A, thecell located above numeral 46 in the data array is not assigned tocarton B if that cell has previously been identified as one that wouldcontact the previous/downstream carton A if that shoe is diverted (asfurther described below). The first cell assigned to carton B is alsoidentified with a lead edge flag in that cell, indicating that the shoerepresented by this cell at time T1 will not only contact carton B ifdiverted, but also is the first shoe assigned to carton B.

Over time, the information in the cells of the upper row of the dataarray will move from right to left in the data array. In other words, attime T2, the information which was in the cell located above numeral 50in the data array at time T1 will be in the cell located above numeral51 in the data array at time T2. Each time interval may correspond tothe amount of time it takes each shoe to advance one shoe width.However, in one embodiment, rather than establishing a time intervalbased on a measured or predetermined speed of the conveying surface, thecentral controller may use the signal from photosensor 28 at firstdivert station 17 to control the shifting of data in the upper row ofcells in the data array. In particular, the information stored in theupper row of cells will shift one cell to the left each time photosensor28 detects, for example, the leading edge of guide pin bearing.Photosensor 28, since it is located at the first divert station prior toany shoes being diverted, is the only divert station photosensor whichwill detect the passage of every shoe. In the embodiment shown,downstream photosensors (e.g., 28′) will not detect the passage of guidepin bearings on shoes which were diverted to the opposite side of apron20 at an upstream divert station.

Following assignment of the lead edge cell for carton B at time T1, ateach subsequent time interval T2, T3, etc. (as measured by the detectionof subsequent shoes by photosensor 28), the cell located above numeral46 will be assigned to carton B until the trailing edge of carton B isdetected by photosensor 161. When the trailing (or rear) edge of cartonB is detected, the cell immediately above numeral 46 in the data arrayis not only assigned to carton B, but also includes a trailing edgeflag. This trailing edge flag indicates that this cell corresponds tothe last shoe which, if diverted, will contact carton B. One or moretrailing cells may also be assigned to carton B, in order to helpprevent a carton from spinning off of the shoes when diverted. In theexample shown in FIG. 3, the control system automatically assigns twotrailing cells to each carton (although any number of trailing cells maybe assigned). Thus, at time T5 (four time intervals after T1), it isseen that five cells are assigned to carton B, one of which includes alead edge flag, and one of which includes a trailing edge flag.

If carton B is designated to be diverted at the first divert station(i.e., corresponding to numeral 50 in the lower row of the data array),as soon as the data array is updated such that the identifier for cartonB is in the cell immediately above numeral 50, central controller 160will send the enable command to local control module 19 at first divertstation 17. Similarly, once the cell immediately above numeral 50 in thedata array no longer includes an identifier for a carton to be divertedat the first divert station (time T9 in the example of FIG. 3), centralcontroller 160 will disable the switch mechanism at the first divertstation.

As also shown in FIG. 3, when the next carton C arrives at the inductionpoint (T5), the cell assignment process is repeated. In this instance,when the front edge of carton C is identified, the cell located abovenumeral 46 in the data array at that time is already assigned to cartonB. If that cell were not only assigned to carton B, but also included atrailing edge flag, the shoe corresponding to that cell, if diverted,would contact both cartons B and C. In such instance, the control systemwill deem this cell to be “dead” and no carton identifier would beinserted into that cell in the data array (i.e., the identifier forcarton B would be removed).

In the example shown, however, the cell above numeral 46 at time T5 whenthe leading edge of carton C is detected is merely identified as atrailing shoe for carton B (since a trailing edge flag is not present).In this instance, the identifier in the cell above numeral 46 is changedfrom carton B to carton C, and a leading edge flag is inserted. Thus, attime T7, the cell above numeral 48 in the data array is identified tocarton C, rather than carton B, and includes a lead edge flag.

During time interval T8, the photosensor 161 has detected not only thetrailing edge of carton C, but also the leading edge of carton D. Thissituation can occur because the control system is designed to allow forcarton gaps which are less than the width of a single shoe. If carton Cand D are to be diverted at the same divert station, onto the samebranch line, the cell immediately above numeral 46 in the data array issimply reassigned to carton D and identified with the lead edge flag. Onthe other hand, if carton C and D are not supposed to be diverted at thesame divert station, the cell located above numeral 46 in the data arraywill be designated as “dead,” and will include neither an identifier forcarton C nor an identifier for carton D. The next upstream cell (i.e.,the cell above numeral 45 in the data array) is then assigned to cartonD and includes a lead edge flag. A flow chart further describing thecell/shoe assignment process is provided in FIG. 4.

Finally, the take-away conveyors of the branch conveyor lines (15 and15′) may travel at a slower rate than the conveying surface of the shoesorter. Because of this, the branch conveyor lines may sometimes becomebacked up if too many cartons are diverted onto that branch conveyorline. Thus, embodiments of the shoe sorter may include a means forensuring that the branch conveyor lines do not become overloaded withdiverted cartons. If a back up condition is detected, cartons will notbe diverted to that branch conveyor line until the back up condition isno longer present.

The above methods and algorithms can be implemented in a variety ofcomputer or electronic systems having one or more processors,controllers, or circuitry for execution of code, instructions, programs,software, firmware, and the like for carrying out the desired tasks.

The specific illustrations and embodiments described herein areexemplary only in nature and are not intended to be limiting of theinvention defined by the claims. For example, destination detectingdevice 155 and sensor 161 could be combined into a single device whichprovides signals to the central controller. Further embodiments andexamples will be apparent to one of ordinary skill in the art in view ofthis specification and are within the scope of the claimed invention.

The foregoing description of the various embodiments and principles ofthe inventions has been presented for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinventions the precise forms disclosed. Many alternatives,modifications, and variations will be apparent to those skilled in theart. Moreover, although many inventive aspects have been presented, suchaspects need not be utilized in combination, and various combinations ofinventive aspects are possible in light of the various embodimentsprovided above. Accordingly, the above description is intended toembrace all possible alternatives, modifications, combinations, andvariations, and have been discussed or suggested herein, as well as allothers that fall within the principles, spirit, and broad scope of thevarious inventions as defined by the claims.

1. A method for transporting items on a conveyor system, the methodcomprising receiving destinations for a plurality of articles to besequentially transported in a primary conveying direction on a primaryconveyor system, wherein the primary conveyor system comprises pusherelements provided along the primary conveyor system and configured tomove articles in a direction different than the primary conveyingdirection to selectively divert articles to branch destinations off ofthe primary conveyor system; spacing the articles apart on the primaryconveyor system in the primary conveying direction, wherein the spacingof at least two adjacent articles is less than the width of a pusherelement; assigning some of the pusher elements to each article; andproviding a signal based upon the location of an article as it travelsin the primary conveying direction, wherein the signal is configured tomove pusher elements assigned to the article at an appropriate locationalong the primary conveyor system to cause the article to be moved in adirection different than the primary conveying direction and to rotateupon initiation of the movement, to thereby divert the article to theircorresponding branch destinations off of the primary conveyor system. 2.The method as recited in claim 1, wherein if a leading article is to bediverted to a branch destination that is different than an articletrailing the leading article, keeping inactive the pusher elementadjacent the trailing edge of the leading article.
 3. The method asrecited in claim 1, further comprising providing memory locationsrepresenting locations along the primary conveyor system; and assigningmemory locations to first and second articles based upon the location ofthe first and second articles along the primary conveyor system, whereinthe first article is adjacent to and downstream from the second articleand spaced from the second article by less than the width of a pusherelement.
 4. The method as recited in claim 3, further comprisingdetermining if the second article adjacent the first article is to bediverted to a different branch destination than the first article, andif so, assigning the memory location that would correspond to thetrailing end of the first article to other than the first article;transporting the first and second articles along the primary conveyorsystem; and using the memory location assignments, moving appropriatepusher elements when the first and second articles have reachedcorresponding diverting locations along the primary conveyor system tocause the pusher elements to move the first and second articles and todivert the first and second articles to a branch destination off of theprimary conveyor system.
 5. The method as recited in claim 3, furthercomprising: determining when the first article has been assigned amemory location where it is to be diverted; and moving correspondingpusher elements when the first article has been assigned the memorylocation where it is to be diverted.
 6. The method as recited in claim3, further comprising: sensing when the first and second articles havechanged conveying locations during conveying; changing the memorylocations assigned to the first and second articles as they changelocations during conveying.
 7. The method as recited in claim 1, whereinthe pusher elements comprise at least one of divert shoes and belts of alinear belt sorter.
 8. The method as recited in claim 1, wherein theprimary conveyor system comprises a single diverting mechanism for eachbranch location, wherein the single diverting mechanism is configured toreceive the signal and move all of the assigned pusher elements for anarticle in response to the signal without the need for divertingmechanism for each pusher element.
 9. The method as recited in claim 8,wherein the single diverting mechanism comprises a single track and asingle switch located at each branch destination.
 10. The method asrecited in claim 1, wherein the spacing of the adjacent articles is lessthan five inches in the primary conveying direction.
 11. The method asrecited in claim 1, wherein the spacing of the adjacent articles is nomore than three inches in the primary conveying direction.
 12. Asortation conveyor apparatus for selectively diverting articles from aprimary conveying surface onto one of a plurality of branch lines,comprising: a driven primary conveying surface configured to support andtransport articles thereon; two or more branch lines extending away fromsaid primary conveying surface; a plurality of pusher elements mountedfor movement with said primary conveying surface for selective movementacross said primary conveying surface so as to selectively divertarticles onto said branch lines; activating mechanisms configured tomove said pusher elements across said primary conveying surface, whereina single activating mechanism is configured to move a plurality ofpusher elements; and a control system for selectively operating saidactivating mechanisms, wherein said control system is configured toassign two or more of said pusher elements to each article to bediverted, and to selectively operate said activating mechanisms whensaid assigned pusher elements are located adjacent a predeterminedbranch line for the article to which the pusher elements are assigned,wherein said control system is configured to ensure proper diversion ofarticles when adjacent articles are spaced apart on the primaryconveying surface by a distance which is less than the width of anindividual pusher element.
 13. The apparatus as recited in claim 12,wherein the pusher elements comprise elements of at least one of a shoesorter and a linear belt sorter.
 14. The apparatus as recited in claim12, further comprising a memory, wherein the control system isconfigured to assign memory locations to first and second articles basedupon the location of the articles along the primary conveying surface,and to use the memory locations to operate the activating mechanismswhen the articles have reached appropriate diverting locations, whereinthe second article is upstream from the first article.
 15. The apparatusas recited in claim 14, wherein the control system is configured suchthat if the second article is not to be diverted to the same branch lineas the first article, reassigning the memory location corresponding tothe trailing end of the first article.
 16. The apparatus as recited inclaim 14, wherein the control system is further configured to sense whenthe first article has been assigned a memory location where it is to bediverted and to activate pusher elements when the first article has beenassigned the memory location where it is to be diverted.
 17. Theapparatus as recited in claim 12, wherein each activating mechanism isconfigured to sequentially move the plurality of pusher elements tocause the article to be diverted to rotate upon initial contact with afirst moved pusher element of the plurality of pusher elements.
 18. Theapparatus as recited in claim 12, wherein the control system does notassign a unique identifier to each pusher element.
 19. The apparatus asrecited in claim 12, wherein the spacing distance is less than fiveinches in the primary conveying direction.
 20. The apparatus as recitedin claim 12, wherein the spacing distance is no more than three inchesin the primary conveying direction.
 21. A computerized method forcontrolling a conveyor system, the method comprising receivingdestinations for a plurality of articles to be sequentially transportedalong a primary conveyor system, wherein the primary conveyor systemcomprises pusher elements for diverting articles to branches off of theprimary conveyor system; providing in memory cells representinglocations along the primary conveyor system; assigning cells to firstand second articles based upon the location of the articles along theprimary conveyor system, wherein the first and second articles areadjacent one another; determining if the second article is to bediverted to the same destination as the first article, and if so,assigning a trailing cell assigned to the trailing end of the firstarticle to other than the first article; and using the cell assignments,providing signals to activate pusher elements at corresponding locationsalong the primary conveyor system to divert the first and secondarticles to destinations off of the primary conveyor system.
 22. Themethod as recited in claim 21, further comprising: if the second articleis not to be diverted to the same destination as the first article,designating a trailing cell assigned to the trailing end of the firstarticle as a dead cell assigned to neither the first or second article.23. The method as recited in claim 21, further comprising: determiningif the first article has been assigned a cell where it is to bediverted; and providing the signals to activate the pusher elements whenthe first article has been assigned the cell where it is to be diverted.24. The method as recited in claim 21, further comprising: determiningwhen the articles have changed locations during conveying; changing thecell assignments of the first and second articles as they changelocations during conveying.
 25. The method as recited in claim 21,wherein the first and second articles are spaced by less than the widthof a pusher element, and wherein the signals activate the pusherelements sequentially to cause rotation of the first and second articlesas they are diverted to their destinations.